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Program to find total number of edges in a Complete Graph

  • Difficulty Level : Basic
  • Last Updated : 14 Apr, 2021

Given N number of vertices of a Graph. The task is to find the total number of edges possible in a complete graph of N vertices.
Complete Graph: A Complete Graph is a graph in which every pair of vertices is connected by an edge. 
Examples
 

Input : N = 3
Output : Edges = 3

Input : N = 5
Output : Edges = 10

 

The total number of possible edges in a complete graph of N vertices can be given as, 
 

Total number of edges in a complete graph of N vertices = ( n * ( n – 1 ) ) / 2 
 

Example 1: Below is a complete graph with N = 5 vertices.
 



The total number of edges in the above complete graph = 10 = (5)*(5-1)/2.
Below is the implementation of the above idea:
 

C++




// C++ implementation to find the
// number of edges in a complete graph
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to find the total number of
// edges in a complete graph with N vertices
int totEdge(int n)
{
    int result = 0;
 
    result = (n * (n - 1)) / 2;
 
    return result;
}
 
// Driver Code
int main()
{
    int n = 6;
 
    cout << totEdge(n);
 
    return 0;
}

Java




// Java implementation to find the
// number of edges in a complete graph
 
class GFG {
     
// Function to find the total number of
// edges in a complete graph with N vertices
static int totEdge(int n)
{
    int result = 0;
 
    result = (n * (n - 1)) / 2;
 
    return result;
}
 
    // Driver Code
    public static void main(String []args)
    {
        int n = 6;
        System.out.println(totEdge(n));
    }
 
}

Python 3




# Python 3 implementation to 
# find the number of edges
# in a complete graph
 
# Function to find the total
# number of edges in a complete
# graph with N vertices
def totEdge(n) :
 
    result = (n * (n - 1)) // 2
 
    return result
             
# Driver Code
if __name__ == "__main__" :
 
    n = 6
 
    print(totEdge(n))
 
# This code is contributed
# by ANKITRAI1

C#




// C# implementation to find
// the number of edges in a
// complete graph
using System;
 
class GFG
{
     
// Function to find the total
// number of edges in a complete
// graph with N vertices
static int totEdge(int n)
{
    int result = 0;
 
    result = (n * (n - 1)) / 2;
 
    return result;
}
 
// Driver Code
public static void Main()
{
    int n = 6;
    Console.Write(totEdge(n));
}
}
 
// This code is contributed
// by ChitraNayal

PHP




<?php
// PHP implementation to find
// the number of edges in a
// complete graph
 
// Function to find the total
// number of edges in a complete
// graph with N vertices
function totEdge($n)
{
    $result = 0;
 
    $result = ($n * ($n - 1)) / 2;
 
    return $result;
}
 
// Driver Code
$n = 6;
echo totEdge($n);
 
// This code is contributed
// by Shivi_Aggarwal
?>

Javascript




<script>
 
// Javascript implementation to find the
// number of edges in a complete graph
 
// Function to find the total number of
// edges in a complete graph with N vertices
function totEdge(n)
{
    var result = 0;
 
    result = (n * (n - 1)) / 2;
 
    return result;
}
 
// Driver Code
var n = 6;
document.write( totEdge(n));
 
</script>
Output: 
15

 

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